Why on earth not? Uncontrolled airports can (and sometimes do!) have weather observers.
At least in the US those so called human 'observers' never report visibility in RVR. And all automated stations (like AWSS/ASOS, etc.) mounted at smaller US airports (say class G) never report visibility as RVR. So knowing how practical FAA is they would never use RVR in such case, how Europe handles it might be different.